The key not turning in the door lock cylinder may also be due to a broken retainer wafer. See my writeup linked below, starting with post #13.
Discovery II - Door lock cylinder wafers - Years ago I had the broken lock shaft problem where the lock cylinder would simply spin. I solved that problem by crafting a replacement shaft from a 20d nail. Now I have the opposite problem. The key won't turn in the door lock at all. A locksmith told...